Potassium Sulfate 0-0-51 Water Soluble Fertilizer A Potassium source without Nitrogen for the final phase of the growth cycle. Water-soluble grade potassium sulfate (SOP). Contains 52% K2O and is white in color. Is the highest grade of water soluble and purity and applied as a liquid to the soil. Provides a Cl-free source of K2O with added sulfur. Recommended For: Apple Avocado Blueberry Lemon Orange Pear Pepper